Lipid Interactions and Hydrophobic Properties of Hydrolysable Tannins

Hydrolysable tannins (HTs) are plant specialized metabolites, which have, for example, nutritional and pharmacological properties. Hydrophobicity is a fundamental physico-chemical property used to estimate the potential activities and interactions of different compounds with macromolecules like lipid vesicles. HTs have abundant structural variability and their hydrophobicity likewise varies notably with respect to different structures and functional groups therein.

The partition coefficients of 47 characterized HTs ([Fig. 1]) were measured and structural features affecting the hydrophobicity of the HT structure found [1]. Notably the number of free galloyl groups, conformation of the polyol glucose, substitution of the anomeric position of glucose, molecular weight and the flexibility of the structure had the largest effect on the observed hydrophobicities.

Fig. 1 LogP values of 47 hydrolysable tannins plotted against their molecular weight measured with UPLC showing galloylglucoses/gallotannins, ⁴C₁ glucose core ellagitannins and ¹C₄ glucose core ellagitannins in different series. The numbers refer to Figures 1 and 2 and Table A1 in [1]. The figure has been previously published in [1] and is reused under open access Creative Commons CC BY 4.0 license.

On the basis of these results, the interactions of 13 HTs with biomimetic lipid vesicles from Escherichia coli (E. coli) were studied with high resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy [2]. HT structures that could penetrate into the lipid bilayer were determined by observing the changes in the lipids 1H chemical shifts and calculating the cross-relaxation rates from nuclear Overhauser effect spectroscopy measurements between the lipid protons and aromatic protons of HTs. Additionally, the thermodynamics of the interactions between a wider subset of the 47 HTs and biomimetic lipid vesicles from E. coli were studied with isothermal titration calorimetry (ITC) [3]. Based on both of these studies the prominence of free galloyl groups, flexibility and increased molecular weight was observed.

Authors declare no conflicts of interest.

• References

• 1 Virtanen V, Karonen M. Partition Coefficients (logP) of Hydrolysable Tannins. Molecules 2020; 25: 3691
• 2 Virtanen V, Räikkönen S, Puljula E, Karonen M. Ellagitannin–Lipid Interactions by HR-MAS NMR Spectroscopy. Molecules 2020; 25: 3691
• 3 Virtanen V, Green RJ, Karonen M. Intercation Between Hydrolysable Tannins and Lipid Vesicles from Escherichia coli with Isothermal Titration Calorimetry. Molecules 2022; [Accepted for publication]

Publication History

Article published online:
12 December 2022